Sprinkler base



FIG. 1 is a top plan view of a sprinkler base showing my new design;

FIG. 2 is a right side elevational view thereof, the left side being a mirror image of the right side shown;

FIG. 3 is a rear elevational view thereof; and

FIG. 4 is a front elevational view thereof. 

The ornamental design for a sprinkler base, as shown and described. 